This invention relates to method and apparatus for conveying particulate matter, especially dust or other fine grained matter, from one location to another.
One system for conveying granular material involves the suspension and movement of the material in a pipe by a high velocity air stream introduced at one end of the pipe. Such a pneumatic system suffers from the problem of pressure drop over the length of the conveyor pipe, especially when the pipe is fairly long. Heavier materials fall out of the air stream, leading to clogging of the conveyor pipe. Another problem of such a system is that the granular material is not efficiently conveyed around sharp bends or turns in the conveyor pipe.
A number of systems have been proposed for solving the pressure drop problem, one of which involves the placement of a porous smaller pipe inside a larger conveyor pipe, supplying air under pressure to the smaller pipe, and then supplying the conveyor pipe with granular material to be conveyed. The air moves inside of the smaller pipe and out the openings spaced therealong to carry the granular material inside the larger pipe. This approach, although more efficient than conventional pneumatic systems, has still encountered difficulties in conveying granular material over long distances and around sharp bends in the conveyor pipe. Also, clogging of the conveyor apparatus is still a problem. Exemplary prior art pneumatic conveyor apparatus is disclosed in U.S. Pat. Nos. 481,672, 3,253,865 and 4,220,426.